Orion In Wild Riders

Hi there, so this came up the other evening. My opponent was playing with Orion and had him in a unit of Wild Riders. Now not knowing a lot about him I looked up his rules and noticed he's not mounted. According the the only relevant rules I can find only mounted characters can join Fast Cav units.

Now in the Wood Elf book you see pictures of wood elf armies with Orion in units of wild riders and the fluff suggests that he is accompanied by the wild riders.

Can anyone show me where the rules allow him to go into a unit please?

As for the picture, based on that logic, you can take Empire Knights in Brettonian units (see the Brett army picture in the BR. As for the fluff thing, I agree, and really wish Orion could join them, but its the same with WR characters. The Helm of the Hunt (how much more WRish can you get) is unavailable to them, not being a suit of armour. Stupid, but it's the rules.

No... read it again, differently. Mounted Chars may join Fast Cav, and in doing so the unit remains fast cav. There is nothing saying other Chars cannot join, but if they do then the unit is no longer fast.

yes alot of wood elf players get this wrong mainly because it says if you take dogs with orion you cannot join other units. But since you can never join another wood elf unit, since no unit is unbreakable, this rule is rendered useless. also in the book it has orion in a unit of wild riders. this may be because he could join them in old 6th edition rules.